The present invention relates to a thermal development type diazo copying material.
A conventional thermal development type diazo copying material comprises a support material, such as paper or a film material, and a photosensitive layer formed on the support material, which photosensitive layer comprises a diazo compound, a coupling component and an auxiliary coloring agent.
In one conventional thermal development method, development is performed by the application of heat at temperatures ranging from 150.degree. C. to 200.degree. C. to a diazo copying material of the above-mentioned type which contains as an auxiliary coloring agent, for instance, urea or sodium trichloroacetate, by which heat application an alkaline material, such as ammonia gas or sodium hydroxide, is produced.
In another conventional thermal development method which is an improvement of the above-mentioned development method, development is performed by the application of heat at temperatures ranging from 90.degree. C. to 130.degree. C. to a diazo copying material of the same type as mentioned above, which contains as an auxiliary coloring agent a higher fatty acid amide, which is melted by the heat application and activates the diazo compound and coupling contained in the diazo copying material. An advantage of this thermal development diazo copying material is that development can be done at lower temperatures than in the case of the first described thermal development diazo copying material. However, its disadvantage is that the thermal development diazo copying material easily deteriorates before use during storage and cannot be preserved for a long period of time.
In these conventional thermal development methods, moreover, higher development temperatures are required than the development temperatures required for a dry type diazo copying material to which ammonia gases are applied from the outside for development.
Further, in the conventional thermal development methods, in the choice of diazo compounds, priority is given to heat resistance rather than to the capability of obtaining high image density. Somehow the diazo compounds which are durable at high temperature cannot yield high image density.
Still further, in the conventional thermal development methods, a heat application apparatus capable of applying heat at such high temperatures to the thermal development diazo materials, with the temperatures being accurately controlled within .+-.10 degrees, is required, but such heat application apparatus is costly. The temperature range of .+-.10 degrees is not at all large in this field. A copying machine employing such a thermal development type diazo copying material is usually used at room temperature, and the difference between the development temperatures and room temperature is so great that it is difficult to control the temperatures within the range of .+-.10 degrees, in particular, when a large number of copies are made continuously or when only a few copies are made at each start-up.
As a matter of course, if the development temperatures are not controlled within the above-mentioned range, development is insufficiently done or excessively done, causing discoloration.
For the above reasons, the thermal development type diazo copying materials are not popular in the field of diazo copying materials, although the thermal development type diazo copying materials have advantages in that they can provide dry copies by use of a simple development apparatus, and in that the copying machines employing the thermal development type diazo copying materials can be reduced in size in comparison with other conventional diazo copying machines.